The present invention relates to apparatus for producing a signal responsive to the transmission of objects, and to a method of determining the light transmission in each of a succession of objects. The objects can be of any suitable type, without limitation, for instance substantially transparent foodstuffs such as sweets, or glass or plastics material articles--the objects can be natural or synthetic.
For instance, sweets could have unwanted inclusions such as bubbles or pieces of opaque foreign matter, or non-homogeneous colourant.
The quality of substantially transparent objects may be affected, usually detrimentally, by the presence of light-absorbing or light-scattering impurities or defects which generally reduce the light transmission in the object.
In general terms, it is desirable to provide means for quantitatively assessing the light transmission in objects, and it is also desirable that the assessment be performed rapidly so that the objects can be sorted automatically into categories according to their light transmissivity or transparency.